A proposal is made to analyze, by genetic and molecular techniques, a human gene whose expression is essential for normal neuroectodermal development. The research undertaken in this proposal will be directed towards the analysis of a human developmental gene, incontinentia pigmenti (IP). IP is an X-linked dominant, hemizygote lethal disorder. IP carrier females are identifiable and present with characteristic neuroectodermal developmental abnormalities. The IP locus has been tentatively localized to Xp11.21. This proposal provides for analysis of the IP locus by linkage analysis using collected genomic DNA samples from multigenerational IP families and characterized human X chromosomal probes capable of detecting restriction fragment length polymorphisms (RFLP's). An assemble collection of somatic cell hybrids containing rearranged X chromosomes will be used to isolated and map cloned X chromosomal fragments capable of detecting RFLP's, to the IP region. We propose to molecularly delineate the IP locus by identifying breakpoints of rearranged X chromosomes associated with the IP phenotype. Constructed somatic cell hybrids containing IP X/autosomal translocations will be used to identify X chromosomal overlaps, deletions, or breakpoint heterogeneity among the IP translocations by Southern blot analysis and pulse field gradient electrophoretic restriction mapping techniques. X chromosomal DNA fragments from the delineated Ip locus will be cloned. Unique, highly conserved regions from the IP locus will provide DNA fragment candidates for the isolation of the IP gene. These analyses will provide information to further delineate the genetic and chromosomal localization of a human developmental gene and provide the necessary starting point for cloning the IP gene. A more thorough understanding of neuroectodermal development, human developmental processes, genes and gen products necessary for normal completion of developmental process, and mutations that disrupt these processes should result from these studies.